The specific, shielded, two-pair cabling that connects two ends of a T1 connection
SONET (Synchronous Optical Network)
A standard for connecting fiber-optic transmission systems. SONET was proposed in the mid-1980's and is now an ANSI standard. SONET defines interface standards at the Physical layer of the OSI seven-layer model.
Synchronous Digital Hierarchy (SDH)
European fiber carrier standard equivalent to SONET.
A device that merges information from multiple input channels to a single output channel.
on the other end of the connection split the individual connections back out.
Frequency Division Multiplexing (FDM)
A process of keeping individual phone calls separate by adding a different frequency multiplier to each phone call, making it possible to separate phone calls by their unique frequency range.
The process of connecting two phones together on one circuit.
The connection between a central office and individual users in a telephone system.
A leased-line connection capable of carrying data at 1,544,000 bps.
The specific, shielded, two-pair cabling that connects the two ends of a T1 connection
CSU/DSU(Channel Service Unit/Data Service Unit)
A piece of equipment that connects a T-carrier leased line from the telephone company to a customer's equipment (such as a router). It performs line encoding and conditioning functions, and it often has a loopback function for testing.
The digital signal rate created by converting analog sound into 8-bit chunks 8,000 times a second, with a data stream of 64Kbps. This is the simplest data stream (and the slowest rate) of the digital part of the phone system.
The signaling method used by T1 lines, which uses a relatively simple frame consisting of 25 pieces: a framing bit and 24 channels. Each DS1 channel holds a single 8-bit DS0 data sample. The framing bit and data channels combine to make 193 bits per DS1 frame. These frames are transmitted 8000 times/sec, making a total throughput of 1.544 Mbps.
Time Division Multiplexing (TDM)
The process of having frames that carry a bit of every channel in every frame sent at regular intervals in a T1 connection.
Fractional T1 access
A service provided by many telephone companies when customers can purchase a number of individual channels in a T1 line in order to save money.
A leased-line connection capable of carrying data at 44,736,000 bps.
The European counterpart of a T1 connection that carries 32 channels at 64 Kbps for a total of 2.048 Mbps-making it slightly faster than a T1.
The European counterpart of a T3 line that carries 16 E1 lines (512 channels), for a total bandwidth of 34.368 Mbps-making it a little slower than an American T3.
High-Level Data Link Control (HDLC) protocol. Used by SONET and E1
American National Standards Institute
Optical Carrier (OC)
Specifications used to denote the optical data carrying capacity (Mbps) of fiber-optic cables in networks conforming to the SONET standard. The OC standard is an escalating series of speeds, designed to meet the needs of medium-to-large corporations. SONET establishes OCs from 51.8 Mbps (OC-1) to 39.8 Gbps (OC-768).
Synchronous Transport Signal (STS)
Signal method used by SONET. It consists of the STS payload (which carries data) and the STS overhead (which carries the signaling and protocol information).
The first generation of packet-switching technology, enables remote devices to communicate with each other across high-speed digital links without the expense of individual leased lines.
An extremely efficient data transmission technique used to send digital information such as voice, data, LAN, and WAN traffic quickly and cost-efficiently to many destinations from one port.
Asynchonous Transfer Mode (ATM)
A network technology that runs at speeds between 25 and 622 Mbps using fiber-optic cabling or CAT 5 or better UTP.
Multiprotocol Label Switching (MPLS)
A router feature that labels certain data to use a desired connection. It works with many type of packet switching (even Ethernet) to force certain types of data to use a certain path.
Public Switched Telephone Network (PSTN)
Also known as Plain Old Telephone Service (POTS). The most common type of phone connection, which takes your sounds, translated into an analog waveform by the microphone, and transmits them to another phone.
Universal Asynchronous Receiver/Transmitter(UART)
A device inside a modem that takes 8-bit-wide data and converts it into 1-bit-wide digital data and hands it to the modem for conversion to analog data. The process is reversed for incoming data.
One analog cycle on a telephone line.
Bearer Channel (B Channel)
A type of ISDN channel that carries data and voice information using standard DS0 channels at 64 Kbps.
Delta Channel (D Channel)
A type of ISDN line that transfers data at 16 Kbps.
ISDN (Integrated Services Digital Network)
The CCITT standard that defines a digital method for telephone communications. Originally designed to replace the current analog telephone system. ISDN lines have telephone numbers and support up to 128-Kbps transfer rates. ISDN also allows data and voice to share a common phone line. Never very popular, ISDN is now relegated to specialized niches.
Basic Rate Interface (BRI)
The basic ISDN configuration, which consists of two B channels (which can carry voice or data at a rate of 64 Kbps) and one D channel (which carries setup and configuration information, as well as data, at 16 Kbps)
Primary Rate Interface (PRI)
A type of ISDN that is actually just a full T1 line carrying 23 B channels.
Terminal Adapter (TA)
The most common interface used to connect a computer to an ISDN line.
Symmetric DSL (SDSL)
Type of DSL connection that provides equal upload and download speed and, in theory, provides speeds up to 15 Mbps, although the vast majority of ISP provide packages ranging from 192 Kbps to 9 Mbps.
Asymmetric Digital subscriber Line (ADSL)
A fully digital, dedicated connection to the telephone system that provides download speeds up to 9 Mbps and upload speeds of up to 1 Mbps.
DSL Access Multiplexer (DSLAM)
A device located in a telephone company's central office that connects multiple customers to the Internet.
Point-to-Point Protocol over Ethernet (PPPoE)
A protocol that was originally designed to encapsulate PPP frames into Ethernet frames. Used by DSL providers to force customers to log into their DSL connection instead of simply connecting automatically.
Real-Time Transport Protocol (RTP)
Protocol that defines the type of packets used on the Internet to move voice or data from a server to clients. The vast majority of VoIP solutions available today use RTP.
Session Initiation Protocol (SIP)
A signaling protocol for controlling voice and video calls over IP. SIP competes with H.323 for VOIP dominance.
A VoIP standard that handles the initiation, setup, and delivery of VoIP sessions.